The victims are all believed to have been living in the Gage Park house and some of them were related, according to detectives.

It is the deadliest single act of violence in Chicago in more than 13 years, but what happened on California Avenue is not answered by any red flags in the public record. The property was in foreclosure as of late last year; owned by a grandfather in his early 60's and his son in his late 30's, according to an attorney who represented them.

Despite the foreclosure, the family that lived here had been making payments and was trying to work it out with the bank, according to their attorney. They previously owned other property in the city as well.

The older couple and the son were Mexican, described by the lawyer as "responsible" and "nice". The son worked for an import company on the South Side and has children of his own. They, along with the children's mother, appear to have been living in the home at the time.

The Gage Park neighborhood is not known as a high-crime section of the city, and last year was not even in the top 30 for overall crime according to police statistics. These were the first murders in Gage Park this year.

The manner of attack was also unusual. According to police statistics, knife murders make up between five and nine percent of the total killings citywide. So far this year, of 63 murders in Chicago, only two involved knives before today.

Gage Park is not known as a particularly heavy gang area, although there are three street gangs that have divided up Gage Park and claim it their turf. But there is no indication this was a gang hit according to police, and a knife attack like this certainly wouldn't fit any gang crime pattern.

But until police verify the identities of the 12-year-old boy, the woman and four men, much of this story remains a mystery.